1. Field of the Invention
The invention relates to a method and an appliance for detecting, identifying and relocating defects in a material strip of great length.
2. Description of the Related Art
During the production of paper, steel and plastics, for example, the material produced is released from the manufacturing machines in great lengths. In endless processes of this nature, the strip material produced is generally examined by an optical inspection system to search for flaws or defects, such as for example, surface defects. If a defect is discovered, the material strip which is coming out of the manufacturing machine cannot generally be stopped in order for an area of material containing the defects to be cut out, since the production operation is not to be interrupted. Consequently, in the event of a defect being detected, the corresponding location on the material strip is merely marked, so that this location can be relocated subsequently. To unload the manufacturing machine, the material strip is collected in relatively large quantities, for example, by being wound up into reels of material. After a relatively large amount of material has been collected, the material strip is severed, and the collected material strip is removed, for example, as a reel.
When the strip is subsequently reversed, for example, by being rewound, these marked locations can then be approached again, rechecked and, if appropriate, cut out. The marked locations are generally approached manually, to ensure that no marks are overlooked.
However, in the case of long strips, manually approaching the marked locations is very time-consuming and laborious. The material strip has to be unwound at a medium speed and has to be checked by an operator for possible marks. Although in principle it is possible for the reels of material strip collected during unloading to be provided with corresponding identifiers in order to indicate the presence and the position indicator of defects, since the reels of material strip are generally of different lengths, since they may be larger or smaller according to the production operation requirements and, in particular, in some cases pieces of undefined length have already been cut off the strip prior to the rewinding, in order to take specimens or remove irregular areas at the end of the material strip, such markings are insufficient to enable the position of the defects to be accurately determined. Consequently, it is currently necessary for the strip material to be manually unwound with care and checked for possible marks.
EP 0 303 722 A1 reveals a method and device for recording and treating defects in webs of material, in which a defect is registered by its position in an X-direction being recorded by a mark placed on the web of material and by at least one further position indicator being recorded together with an identification of the mark being recorded. Further position indicators determined and stored are X-Y-coordinates of a family of points which fix a boundary line around the defect, the mark or a side edge of the material web serving as a reference point for these X- and Y-coordinates.
DE 33 15 125 C1 has disclosed an arrangement for marking defect locations on webs of material, in which the web of material is guided past a defect-recording scanning device and a marking device which is at a distance therefrom. Signals from the defect-recording scanning device are successively analyzed to check whether they are defect or structure signals, the defect signals determined being stored together with their coordinates on the web. At intervals, it is checked whether there is a defect signal in the memory concerning the longitudinal coordinate which is in the process of moving past the marking device, and if such a signal is present a marking is made at the corresponding coordinates on the web.
The primary objects of the invention reside in providing a method and a device for detecting, identifying and relocating defects in a material strip of great length, in which detected defects can be relocated reliably and quickly with relatively little effort.
According to one aspect of the invention, there is provided a method in which a material strip is checked for defects, and position indicators are applied to the material strip continuously over its length. In the event of a defect being observed, an associated defect position indicator is stored, and during the subsequent relocation of a surface defect, a current starting position indicator is established and the material strip is moved over a conveying length which is calculated from the established starting position indicator and the stored defect position indicator.
The invention furthermore provides a device comprising an optical inspection device for observing a defect, a marking device for marking the material strip, whereby position indicators can be applied continuously to the material strip, and a memory device whereby measurement data from the optical inspection device can be recorded and can be stored together with the associated position indicator.
Further objects, features and advantages of the invention will become apparent from the detailed description of preferred embodiments that follows when considered together with the accompanying figures of drawing.